Researchers redefine the old ‘scratch test’
It might not seem like scraping the top of a cold stick of butter with a knife could be a scientific test, but engineers at MIT say the process is very similar to the “scratch test,” perhaps the oldest known way to assess a material’s hardness and strength — or, in scientific language, its resistance to deformation. Using the scraping of butter as a starting point, the MIT engineers launched a study to see if the age-old scratch test — used by researchers to gauge a material’s properties by indenting or scratching it with a tool — could be used to determine a material’s toughness, or how well it resists fracturing after a small crack has already formed. The answer: The scratch test does indeed measure crack resistance rather than strength, meaning that engineers now have a simple “new” test for assessing a material’s fracture properties.“Fracture mechanics has not reached...